Electronic control circuit

ABSTRACT

An electronic control circuit for use with a heater, a fan, a humidifier or any device utilizing a power mode switch and a condition sensor, the electronic control circuit including a single control switch for controlling both power output and responding to a sensed condition. The electronic circuit includes a microprocessor, preferably in the form of an application-specific integrated circuit to provide the circuit logic. The single control switch is preferably a push-button switch which places the unit in the selected mode of operation. The electronic control circuit also includes a thermistor or humidity sensor to sense conditions and, depending upon the set temperature/humidity by the control switch and the sensed condition the unit will operate accordingly. The unit can also operate in a manual mode, thereby bypassing the sensor operation.

PRIORITY APPLICATIONS

[0001] This application claims the benefit of U.S. patent applicationSer. No. 09/844,995 filed on Apr. 27, 2001. This application also claimsthe benefit of U.S. Provisional Application No. 60/200,586 filed on Apr.22, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an improved electronic controlcircuit, and more particularly, to an electronic control circuit whichprovides the functions of a multi-position power switch and a sensordevice to control operation of an apparatus.

[0004] 2. Description of Prior Art

[0005] Presently available electric space heaters and electric fans fordomestic use are generally provided with at least two controlcomponents. The first control component is a multi-position power switchto select a proper setting, e.g. off/high/medium/low. The second controlcomponent is a thermostat to de-energize the device when apredetermined, pre-set temperature value is achieved. Likewise currentlyavailable humidifiers are provided with a similar multi-position powerswitch and, rather than a thermostat, are provided with a humidistat tosense when a predetermined, pre-set humidity level is achieved.

[0006] The present multi-position power switches and mechanicalthermostats/humidistats are expensive, unreliable, and mechanicallycomplex. Additionally, these components constitute as a major portion ofthe cost and complexity in making and using low cost heaters, fans andhumidifiers. Furthermore, the mechanics of these components tend torender them the most oft failed components in the device. Morespecifically, each component requires a control knob and individualwiring connections, which are labor intensive and points of potentialfailure.

OBJECTS AND SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide an electroniccontrol device in a heater, a fan or a humidifier which eliminates theuse of complex switches and reduces wiring connections to improvereliability.

[0008] It is yet a further object of the present invention to provide anelectronic control device in a heater, a fan or a humidifier which issimple to construct thereby reducing complexity of construction andlowering the cost of same.

[0009] It is yet a further object of the present invention to provide anelectronic control device in a heater, a fan or a humidifier whichimproves the reliability of the operation.

[0010] It is still another object of the present invention to provide asolid state electronic control device which uses a single actuator toset a desired operating level (high, medium, or low) as well as apredetermined temperature/humidity value at which power to the unit isto be terminated.

[0011] It is another object of the present invention to provide anelectronic control circuit for use in a heater, a fan or a humidifierwhich uses a single push button to both turn the unit on, set anoperating power level and set a predetermined thresholdtemperature/humidity value to achieve by operation of the unit.

[0012] In accordance with one form of the present invention, anelectronic control circuit is provided for operating a device such as aheater, a fan, a humidifier or any other device which includes anoperating power level and a pre-set value for comparison with a sensordevice. The electronic control circuit includes a single control switchfor turning on the device and selecting a mode of operation. The mode ofoperation includes both a power level of operation and one of aplurality of pre-set values. The sensor is provided for sensing acondition. The electronic control circuit further includes a comparatorfor comparing the sensed condition to the selected preset value. Theelectronic control circuit includes a means for providing operatingpower to the device in response to an output from the comparator. In apreferred embodiment, the single control switch is a push-button switch.Furthermore, the means for providing operating power to the deviceincludes an application-specific integrated circuit.

[0013] In one embodiment, the electronic control circuit is used in anapparatus for modifying ambient air conditions. The apparatus includes ahousing, a fan assembly positioned within the housing and including amotor and a fan blade attached to the shaft of the motor. The apparatusfurther includes an electronic control circuit electrically coupled tothe motor and adapted to provide power thereto. The electronic controlcircuit has a single switch to turn on operating power to the apparatusand to select a pre-set threshold ambient air condition. The electroniccontrol circuit further includes a sensor for sensing an ambient aircondition and a means for comparing the pre-set threshold ambient aircondition to the sensed ambient air condition. The electronic controlcircuit provides power to the fan assembly motor to substantiallyachieve the pre-set threshold ambient air condition in view of an outputof the comparing means and terminates power to the fan assembly motorwhen the pre-set threshold ambient air condition is substantiallyattained. Preferably, the switch is a push-button switch and theelectronic control circuit includes a plurality of discretelyincremented pre-set threshold ambient air condition values which can beselected by repeatedly activating the switch. The apparatus furtherincludes indicia, such as light emitting diodes, to indicate both thepower level of operation and the selected pre-set threshold ambient aircondition.

[0014] The logic for the electronic control circuit is provided by anapplication-specific integrated circuit to control power to theapparatus motor and to illuminate the indicia associated with the modeof operation. The sensor may comprise a thermistor in the case of a fan,a heater, a griddle, or the like or a humidity sensor for use with ahumidifier. With respect to humidifiers, the electronic control circuitcan be used with either a cool mist humidifier which utilizes a fan anda wick filter immersed in a pool of water or with a warm mist humidifierwhich includes a heating element for creating steam to be released tothe surroundings.

[0015] The present invention is also directed to a method of operatingan apparatus for modifying an ambient air condition. The apparatusincludes either a heating element or a fan assembly wherein the fanassembly includes a motor and a fan blade coupled to the shaft of themotor. The electronic control circuit is electrically coupled to eitherthe heating element or the fan motor, or both, for providing operatingpower thereto. The electronic control circuit includes a single controlswitch and a sensor for sensing an ambient condition. The apparatus isoperated by actuating the single control switch to turn on the apparatusand to select an operating power level and a pre-set threshold ambientair condition value. The pre-set threshold ambient air condition iscompared to the sensed ambient air condition and operating power isprovided to the heating element, the motor or both if the sensed ambientair condition is not substantially similar to the pre-set ambient aircondition. Power is terminated to the device when the sensed ambient aircondition is substantially similar to the pre-set threshold ambient aircondition. The method further includes repeatedly actuating the switchto progress through a plurality of operating modes and pre-set thresholdambient air condition values.

[0016] A preferred form of the electronic control circuit, as well asother embodiments, objects and advantages of this invention, will beapparent from the following detailed description of the illustrativeembodiments thereof, which is to be read in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a perspective view of a heater including a firstembodiment of the electronic control device of the present invention.

[0018]FIG. 2 is a cross-sectional view of the heater illustrated in FIG.1.

[0019]FIG. 3 is an electrical schematic of the electronic controlcircuit for the heater illustrated in FIGS. 1 and 2.

[0020]FIG. 4 is an electrical schematic of the electronic controlcircuit for use with a box fan.

[0021]FIG. 5 is an electrical schematic of the electronic controlcircuit for use with a window fan.

[0022]FIG. 6 is an alternative embodiment of the heater formed inaccordance with the present invention.

[0023]FIG. 7 is an electrical schematic of the electronic controlcircuit for the heater illustrated in FIG. 6.

[0024]FIG. 8 is an electrical schematic of the electronic controlcircuit of the present invention utilizing a standard microcontroller.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Referring to FIG. 1, a heater is shown utilizing a firstembodiment of the electronic control device of the present invention.Although, FIG. 1 illustrates a heater, it is envisioned that theelectronic control circuit of the present invention is equally adaptableto be used in a fan including a thermostat or a humidifier including ahumidistat. For example, the same device illustrated in FIG. 1 may beoperated as a fan with a thermostat by removing the heating element fromthe unit. A typical structure for a window fan including a thermostat isdisclosed in commonly owned U.S. Pat. No. 5,660,605 entitled “WindowFan”, the disclosure of which is incorporated herein by reference.Likewise, a cool mist humidifier may be operated which uses a wickfilter and a fan to draw air through the filter to add moisture to thesurroundings using a similar electronic control circuit. The structureof a cool mist humidifier is disclosed in commonly owned U.S. Pat. No.5,529,726 entitled “Evaporative Humidifier”, the disclosure of which isincorporated herein by reference. Similarly, the electronic controlcircuit can be employed in a warm mist humidifier having a humiditysensor. A typical structure for a warm mist humidifier is disclosed incommonly owned U.S. Pat. No. 5,792,390 entitled “Humidifier with TopFill Tank” the disclosure of which is incorporated herein by reference.It is also contemplated that the single-button electronic controlcircuit disclosed herein is also capable of operating any type of unitwhich requires both power level control and achieving a set temperature,such as an electric cooking device. For example, the electronic controlcircuit of the present invention is useful in controlling an electricgriddle which includes a heating element and set temperature value.

[0026] In this first embodiment, the electronic control circuit includesa single switch, namely a push-button switch having a manual andautomatic mode of operation. It is also envisioned that other types ofswitches can be used, however, a push-button switch allows for easyoperation and is low in cost. More specifically, in the manual mode, thedevice, e.g. a heater, a fan or a humidifier, can be operated at eitherhigh, medium, or low power regardless of the ambient temperature orhumidity level. Alternatively, the device may be operated in anautomatic mode based upon a sensed temperature/humidity and apredetermined threshold temperature or humidity set point or value setby the user. For example, in the case of a heater, the automatic modemay include a temperature set point of 70° F. If the unit is set inautomatic mode to 70° F., the heater will operate at a selected powerlevel, until ambient temperature sensed by a thermostat reaches 70° F.Once the set point temperature is attained, the electronic controldevice of the present invention de-energizes the unit until the sensedtemperature once again falls below the set point temperature and theunit is once again turned on. As noted earlier, the same type ofelectronic control circuit is equally applicable to a fan equipped witha thermostat or a humidifier equipped with a humidistat.

[0027] Referring again to FIG. 1, the heater 10 includes a push-buttonswitch 12 to operate the electronic control circuit. A series oflight-emitting diodes (LED's) 14 are provided around the periphery ofthe push-button switch 12 to provide a visual indication as to the modeand setting of operation of the unit. The single push-button switch andassociated circuitry replaces the functions of previously usedmulti-position switches and thermostats/humidistats.

[0028]FIG. 2 is a front cross-sectional view of FIG. 1 illustrating thecomponents of the heater 10. The heater includes a heater housing 15 forsupporting therein a fan assembly comprising a motor 16 and a fan blade18. The motor 16 includes a shaft (not shown) which is mechanicallyconnected to the center hub of the fan blade to rotate the bladeproducing air flow which exists the front grille. It is envisioned thatthe fan assembly may take any known form so long as air is drawn acrossthe heating element for discharge to the surroundings. The heater 10also includes a heating element 20 to produce the heated air to bedischarged from the unit. In this illustration, the heating element isin the form of a circular element, however, many different types ofheating elements may be used as is well known by those of ordinaryskill.

[0029] The heater 10 uses an electronic control circuit to operate theheating element and fan. As illustrated in FIG. 2, the electroniccontrol circuit is preferably in the form of a printed circuit board 22having a logic circuit in the form of an application-specific integratedcircuit (ASIC) 24 programmed to perform the specific logic of theelectronic control circuit to operate the heater. The ASIC 24 iselectronically coupled to both the heating element and fan motor viaprinted traces on the circuit board as well as wires, 26 and 28,respectively. The electronic control circuit also includes a thermostat30 coupled to the ASIC 24 via wires coupled to the printed circuit board22. The thermostat 30 senses ambient air temperature and provides theinformation to the microprocessor for comparison to the predeterminedthreshold temperature set by the user via the push-button switch.

[0030]FIG. 3 illustrates the electronic control circuit for use with aheater. The ASIC U1 is a collection of logic circuits having thespecific logic required for operation provided therein. A suitable ASICis produced by The Holmes Group, Inc., a Massachusetts Corporation underPart No. “Holmes Accutemp ASIC”.

[0031] Furthermore, the ASIC includes a comparator for comparing thesensed ambient temperature/humidity value to the pre-set value selectedby the user. The electronic control device circuit also includes a triactrigger circuit to provide power to the unit being operated. Contrary toa microprocessor which can be programmed to perform a variety offunctions, the ASIC is designed to perform the specific functions forwhich it is programmed. Accordingly, ASIC's are typically lower in unitcosts and provide higher performance by eliminating the circuit from thechip needed to make it programmable and incorporating just those logicfunctions needed for the application. The higher performance comes fromdirectly implementing the logic instead of using an instruction setrequiring multiple clock pulses to execute.

[0032] As illustrated in FIG. 3, the heater uses a single push-buttoncontrol switch S1 to control operation of the unit and seven (7) LED'sto indicate the mode of operation. Naturally, other types of controlswitches and varying numbers of LED's may be used depending upon thenumber of modes and settings chosen by the designer. The ASICmicroprocessor U1 uses the input A/C power from a standard 120 volt, 60Hz outlet to perform timing functions and to determine when to fire atriac Q1 that controls operation of the heating element and fanassembly. The input power is provided to the electronic control circuitvia pads J2 and J3 on the printed circuit board. The hot A/C input ispassed through a power supply rectifier which includes components D1 andR5 arranged as shown in FIG. 3. It should be noted that diode D1 isarranged to provide negative voltages to the ASIC U1 at pin 9 labeledVSS. Resistor R5 provides current regulation and resistor R4 provides asample of the AC line frequency to determine when to fire the triac andfor internal timing function. The A/C neutral is provided to the pin 1,VCC, of the ASIC U1. Negative going pulses on pin 15 labeled TRIAC ofthe ASIC U1 fire the triac Q1. The A/C neutral is also provided to thetriac Q1. Capacitor C1 protects the ASIC from transients on the A/Cpower line. Capacitor C2 acts as a filter capacitor for the power supplyto reduce ripple thereon.

[0033] The ASIC U1 further includes an internal oscillator, whosefrequency is determined by an external RC network, R2 and C5 coupled topin 11. The RC network is used to generate a higher frequency foroperations that require smaller time increments than can be obtainedfrom the input 60 Hz line through pin 16 labeled CLOCK. The electroniccontrol circuit has been engineered to draw a relatively constantcurrent, regardless of the mode of operation. Therefore, no voltageregulation is required. Furthermore, by changing the value of resistorR2, the frequency of the internal oscillator can be changed therebydelaying the firing of the triac in the low power mode of operation.Thus, the ASIC U1 can be used in a wider range of applications.

[0034] The electronic control circuit further includes a thermistor T1coupled to the ASIC microprocessor U1 via printed circuit board pads J4and J5. Capacitors C6 and C7 along with thermistor T1, set the frequencyof an oscillator inside the ASIC. As the temperature changes the valueof thermistor T1, the oscillator frequency changes thus enabling theASIC to measure temperature.

[0035] The ASIC U1 also includes outputs to each of the LED indicatorswhich provide visual indicia as to the mode of operation of the heater.Two LED's provide indication of the power level, either high (D2) or low(D3) and the remaining LED's provide indication as to the predeterminedthreshold temperature at which the heater will be turned on, i.e., 65°F. through 80° F. in 5° increments, D4-D8, respectively.

[0036] As discussed earlier, the ASIC and associated electronic controlcircuit can be used to operate either a heater, a fan or a humidifier.To accomplish this function, the ASIC U1 includes a programming pin thatcan be tied to either the DC power voltage or ground thereby identifyingwhatever the ASIC is operating, a heater or a fan. A similar circuit maybe used in a cool mist humidifier by exchanging the thermistor with ahumidity sensor.

[0037] The ASIC logic also permits the heater to be operated in a manualmode, i.e. constant operation at a selected power level or in an“automatic” mode using the input from the thermistor to determine if theset threshold temperature has been reached and only operate the heaterand fan by firing the triac when the temperature is below or above theset temperature, respectively.

[0038] Operation of the heater using the push-button switch S1 requiresa series of pushes of the switch to proceed through the sequence ofoptions available. When power is first applied to the electronic controlcircuit by plugging the unit into the wall outlet, an internal power onreset circuit in the ASIC turns off all external signals. The first pushof the control button or switch places the heater in manual high powermode lighting the high LED and causing a pulse to fire the triac nearthe zero crossing of the A/C power. In case of a large fan which has alarger fan motor providing an inductive load, a second pulse is alsogenerated approximately 2.2 m sec. after the zero crossing so that thetriac can be turned on when enough holding current is present to keep iton.

[0039] A second push of the control button places the heater in themanual operation low power level mode thereby lighting the low LED. Thetriac is fired with a delay sent by the frequency of the RC oscillatoras determined by the values of resistor R2 and capacitor C5 to place theunit in the low power mode of operation.

[0040] A third push on the control button places the heater in the“automatic” mode at high power. Specifically, the “automatic” mode isdefined as operating to a predetermined set point and comparing the settemperature with the sensed ambient temperature of the thermistor. Thisthird push lights both the high LED and 80° F. LED and sets a thermostattemperature of 80° F. In this mode, when operating as a heatercontroller, the triac fires when sensed ambient temperature is below 79°F. thereby supplying power to the heating element and fan motor. Thetriac does not fire when the ambient temperature is above 81° F. and theheater remains off until the temperature drops below 79° F. If theelectronic control circuit were controlling a fan, the triac would beturned on when the sensed ambient temperature rises above the settemperature and turns off when sensed ambient temperature drops belowthe set temperature. The off and on limits are one degree above andbelow the set temperature to prevent the unit from cycling on and offrepeatedly.

[0041] Subsequent pushes of the control button changes the temperaturesetting in five degree increments as follows: 75° F., 70° F., 65° F.,and 60° F. Following the high power level, 60° F. setting, the next pushcauses the heater to go into the low power level mode and the 80° F.temperature setting. Accordingly, in this setting, the heater operatesat low power to achieve and maintain a sensed ambient temperature of 80°F. Thus, the low LED is lit as well as the 80° F. LED. Subsequent pushesof the control button moves the set temperature through the setincrements at low power levels until the low power, 60° F. mode isreached. The next push on the control button places the electroniccontrol circuit and the ASIC in the “off” mode and turns off all LED'sand stops firing the triac.

[0042] As a matter of convenience, at any time during the settingsequence, if the push button is held down for more than one (1) secondin any mode of operation, the electronic control circuit enters the“off” mode. When the control button is pushed again, the electroniccontrol button is pushed again, the electronic control circuit and ASICreturns to the mode setting it was in prior to being turned off by theprolonged push of more than (1) second.

[0043] Furthermore, as discussed above, the electronic control circuitASIC logic provides for a range of temperature around the set pointtemperature in which the operation of the unit begins and is terminated.More specifically, in the case of a heater, the sensed ambienttemperature must be at least one degree above the set temperature beforethe unit will shut off. Likewise, the temperature must be at least onedegree below the set temperature for the unit to turn on. Otherwise, theunit would turn on and off excessively around the set temperature.

[0044]FIG. 4 is an electrical schematic of an electronic control circuitof the present invention for use with a box fan. Like components fromthe schematic of FIG. 3 have the same reference designations. However,the values for some of the components have been adjusted to be moresuitable for use with the inductive load of a fan. For example,capacitor C7 is no longer needed and an RC network including resistor R1and capacitor C3 has been added in parallel to the firing triac tocompensate for the inductive load of the fan. With respect to operationof the box fan, an identical sequence of activations of the push buttonswitch, i.e. control button, yields identical modes of operation. Itshould also be noted that pin 10 of the ASIC is no longer tied to pin 9and ground thereby operating the ASIC in the “fan” mode rather than the“heater” mode.

[0045]FIG. 5 is an electrical schematic of an electronic control circuitof the present invention for use with a window fan. Once again, likecomponents of different values from FIGS. 3 and 4 have the samereference designation. Since the window fan motor is not a largeinductive load, there is no need for the RC network in parallel with thefiring triac used in connection with box fan application of the circuit.

[0046]FIG. 6 is an alternative embodiment of a heater using the singlecontrol switch and electronic control circuit as illustrated in FIG. 7.In this embodiment, the heater has three power level settings, high,medium and low and an additional temperature setting of 55° F. It iscontemplated as part of the present invention to have any given numberof power level settings as well as any given number oftemperature/humidity settings.

[0047] The heater illustrated in FIG. 6 having the electronic controlcircuit shown in FIG. 7 operates by repeated pushing of the push-buttonthrough the following sequence of operating conditions:

[0048] Originally in “off” position;

[0049] First push, provides continuous operation and a high powersetting regardless of temperature with the corresponding high LEDilluminating;

[0050] Second push provides continuous operation at medium power settingregardless of temperature with the corresponding medium LEDilluminating;

[0051] Third push provides, continuous operation on low power settingregardless of temperature with the corresponding low LED illuminating;

[0052] Fourth push provides operation at a predetermined power levelwhen ambient temperature is less than 55° F.; if sensed ambienttemperature is greater than 55° F., power to the heating element and fanis terminated until sensed ambient temperature falls below 55° F.Subsequent pushes moves the sequence through the incremented temperaturesettings until the 80° F. mode is reached. The next push turns unit off.

[0053] As illustrated in FIG. 6, the LED's are individually labeledaccording to each of the above-identified operating conditions. Only theappropriate LED is illuminated at any given time.

[0054] Although the electronic control circuit may be constructed ofdiscrete logic components, in order to be cost effective and mostreliable, the electronic control circuit of the present invention ispreferably in the form of a printed circuit board including amicrocontroller and more preferably in the form of an ASIC having thedriving software customized thereon.

[0055]FIG. 7 is an electrical schematic of the electronic controlcircuit of an alternative embodiment utilizing an ASIC to achieve thedesired functions. In the electrical schematic of FIG. 7, it is assumedthat the ASIC includes an analog to digital converter and an internaloscillator. The circuit also uses a voltage regulator D1.

[0056]FIG. 8 illustrates a similar electronic control circuit schematicto that of FIG. 7, except that the circuit utilizes a commonly availablemicroprocessor rather than an ASIC. The circuit of FIG. 8 also includesa thermostat/humidistat sensor for sensing ambient temperature/humidityand a triac trigger circuit to provide power to the unit being operated.

[0057] As discussed above, the circuit of FIG. 8 is somewhat morecomplicated including additional electrical components to achieve thesame results as the circuit using the ASIC. However, the operation ofthe circuit would be similar to that described above with respect to theheater circuits shown in FIGS. 3 and 7.

[0058] The electrical components and values illustrated in FIGS. 3, 4,5, 7 and 8 are provided for illustrative purposes only. It iscontemplated that other components arranged in a different manner canaccomplish the functions attained in the present invention and fallwithin the scope thereof.

What is claimed is:
 1. An apparatus for modifying ambient air conditionscomprising: a housing, a fan assembly positioned within the housing andincluding a motor and a fan blade attached to a shaft of the motor; andan electronic control circuit electrically coupled to the motor, andadapted to provide power thereto, the electronic control circuitcomprising a single switch to turn on operating power to the apparatusand to select a pre-set threshold ambient air condition, the electroniccontrol circuit further including a sensor for sensing an ambient aircondition and a means for comparing the pre-set threshold ambient aircondition to the sensed ambient air condition, wherein the electroniccontrol circuit provides power to the fan assembly motor tosubstantially achieve the pre-set threshold ambient air condition andterminates power to the fan assembly motor when the pre-set thresholdambient air condition is substantially attained.
 2. The apparatus asdefined in claim 1, wherein the switch is a pushbutton switch.
 3. Theapparatus as defined in claim 1, wherein the electronic control circuitincludes a plurality of discretely incremented pre-set threshold ambientair condition values.
 4. The apparatus as defined in claim 3, whereineach pre-set threshold ambient air condition value includes indiciaassociated therewith.
 5. The apparatus as defined in claim 4, whereinthe indicia comprises light emitting diodes.
 6. The apparatus as definedin claim 1, wherein the single switch further sets a power level ofoperation.
 7. The apparatus as defined in claim 1, wherein theelectronic control circuit includes an application-specific integratedcircuit to control power to the fan assembly motor and illuminateindicia associated with a mode of operation for said apparatus.
 8. Theapparatus as defined in claim 1, wherein the comparing means comprises acomparator circuit.
 9. The apparatus as defined in claim 1, wherein thesensor comprises a thermistor and said apparatus is a fan.
 10. Theapparatus as defined in claim 1, further comprising a heating elementelectrically coupled to the electronic control circuit and wherein thesensor is a thermistor and the electronic control circuit controlsoperating power to the heating element and motor.
 11. The apparatus asdefined in claim 1, further comprising a wick filter element, whereinsaid housing includes a means for holding water in contact with the wickfilter element, and wherein the sensor comprises a humidity sensor. 12.A method of operating an apparatus for modifying an ambient aircondition, the apparatus including at least one of a heating element anda fan assembly comprising a motor and a fan blade coupled to a shaft ofthe motor, and an electronic control circuit electrically coupled to theat least heating element or motor for providing operating power thereto,the electronic control circuit including a single control switch and asensor for sensing an ambient air condition, the method comprising thesteps of: actuating the single control switch to turn on the apparatusand to select an operating power level and a pre-set threshold ambientair condition value; comparing the pre-set threshold ambient aircondition to the sensed ambient air condition; providing operating powerto the at least heating element or motor if the sensed ambient aircondition is not substantially similar to the pre-set ambient aircondition; and terminating power to the at least heating element ormotor when the pre-set threshold ambient air condition is substantiallysimilar to the sensed ambient air condition.
 13. The method as definedin claim 12, wherein the single control switch is a push-button switchand the step of actuating includes repeatedly pushing the push-button toprogress through a plurality of operating modes and pre-set thresholdambient air condition values.
 14. The method as defined in claim 12,wherein the sensor is a thermistor and the apparatus is operated as afan.
 15. The method as defined in claim 12, further including a heatingelement electronically coupled to the electronic control circuit, theelectronic control circuit providing operating power to the heatingelement, and wherein the sensor is a thermistor and the apparatus is aheater.
 16. The method as defined in claim 12, further including ahousing having a means for holding water and a wick filter in contactwith water in the housing, and wherein the sensor is a humidity sensorand the apparatus is a humidifier.
 17. The method as defined in claim12, wherein the apparatus includes a housing having a means for holdingwater and a heating element for heating the water to form a mist, andwherein the sensor and the apparatus is a humidifier.
 18. An electroniccontrol circuit for operating a device comprising: a single controlswitch for turning on the device and selecting a mode of operationincluding power level and one of a plurality of pre-set values; a sensorfor sensing a condition; a comparator for comparing the sensed conditionto the selected pre-set value; and means for providing operating powerto the device in response to an output from the comparator.
 19. Theelectronic control circuit as defined in claim 17, wherein the singlecontrol switch is a push-button.
 20. The electronic control circuit asdefined in claim 17, wherein the means for providing operating powercomprises an application-specific integrated circuit.